The prior art discloses intermodal vehicles for use in forming a train of highway trailers including leading and trailing trailers interconnected to each other and supported by the intermodal vehicles. The intermodal rail vehicle of the present disclosure may be used with trailers of any configuration, including trailers designed for hauling “ISO” shipping containers. Each of the highway trailers includes a coupler socket assembly at its leading end and a coupler socket assembly at its trailing end. Each socket assembly is provided with a pair of vertically spaced apart aligned apertures for receiving a vertical coupling pin.
The intermodal vehicles are characterized by two lower frame assemblies, each supported by a rail wheel and axle assembly and a one-piece upper rifting frame assembly supported by the two lower frame assemblies by spring means. The spring means includes air springs which are arranged so that when air is evacuated from the air springs, the upper lifting frame will descend toward the lower frame assemblies and when air is added to the air springs, the upper lifting frame will rise and concurrently raise any trailers resting thereon to a height sufficient so that the trailer wheels are clear of the railroad track. In addition to this primary spring means, a secondary spring means is provided so as to support the trailer above the track in the event of failure of the primary air springs. In addition to a horizontal trailer support surface, the upper lifting frame includes a coupler tongue, or drawbar, which is formed to be received in the coupler socket of the trailer.
Each end of the coupler tongue is provided with an aperture for receiving a vertical coupling pin which rises from the upper lifting frame to pass through the coupler socket assembly in the trailer and at the same time pass through the coupler tongue within the socket, thus effecting a connection between the intermodal vehicle and the trailer resting thereon. It is also a feature of the prior art that the lower frames are steerable with respect to the upper frame assembly. The prior art also discloses a transition vehicle or other means for connecting a unit train of intermodal vehicles having a unique coupling system to the “knuckle” couplers found on conventional trains.
A standard wheel set on a railcar consists of a pair of rigid side frames suspended on a spring system with a pair of axles having wheel sets mounted in bearing sets between the side frames. This configuration allows virtually no motion other than the minimal clearance of the wheels and axles relative to the frames or to one another during operation. In this arrangement, although the bogie can pivot on a central bearing, the wheels are unable to follow the contour of the rail curvature or yaw (in general, yaw is defined as the rotation of an object about a vertical rotational axis). The fixed orientation of the bogie axles in the side frames results in lateral forces and wear on the wheels, the wheel flanges, and degradation of ride quality with increasing speed. Degraded ride quality at higher speeds is attributed to a phenomenon known as “hunting,” which describes the periodic sinusoidal yawing motion of the bogie about its center bearing during operation.
This hunting motion is caused by a rail-to-wheel interaction that is especially prevalent as the wheels progress around a corner and can be occasioned by track irregularities that cause the wheel sets to yaw. In certain circumstances, the aforementioned interaction is so severe that it causes the flange of the wheel to climb the rail, causing an aggressive lateral correction or, in extreme cases, a derailment.
Improved ride quality and reduced rail and wheel wear has led to a number of improvements to the wheel set suspensions of rail vehicles. The goal of such improvements has been to create arrangements that constrain or allow the steering of the wheels and axles of the bogie to follow the curvature of the track. A recent development, which was driven by the requirements of high speed passenger rail requirements, has been the articulated bogie, which includes an articulation joint between the two lower frames that allows steering of the bogie.
In general, rail bogies can be divided into three groups based on the energy source of the mechanism that controls steering at the articulation joint between two articulated wheel portions of the bogie. A first group includes wheel sets yawed by contact forces between the rail and the wheels of the bogie. In a second group, wheel sets are yawed by the relative rotation between the bogie frame and vehicle body. Bogies in this second group can exhibit either yaw or roll, and typically utilize a system of links or levers to steer the trailing wheel set by the leading wheel set. One example of this type of bogie is commonly referred to as the Sheffel bogie, which uses a series of levers connected to one axle set to cause the rotation of the second axle set. In a third group of bogies, the wheel sets of the bogie are actively yawed by an external energy source, for example, by use of electric, hydraulic, or pneumatic actuators.
The prior art has validated the idea of making a train of highway trailers with steerable intermodal vehicles which permit the make-up of a train without the need for cranes or other lifting devices; however, these prior intermodal vehicles are unnecessarily complex and it is beneficial to the art to provide a simplified intermodal vehicle of an improved design which corrects some of the weaknesses and complications found in the prior art.